Cleaning and preserving of metallic surfaces



252. COMPOSITIONS,

Patented June 2, 1931 UNITED STATES Examiner PATENT OFFICE DEAL H. TOMIPKINS, OF NITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO CLEANING AND PRESERVING OF METALLIC SURFACES No Drawing.

The present invention relates to the cleaning and preservation of metallic surfaces, wherein the metal is in contact with a liquid of an acid nature. More particularly, the

invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to a pickling process.

Certain objects of the invention are to prevent to as great an extent as possible the acid pickle liquor from attacking clean portions of the surface of a metal; to obviate over-pickling, embrittlement and pitting of the articles treated; to minimize the amount of metal lost in pickling; to increase the efficiency of the pickling operation and to prolong the effective life of the pickling bath and particularly to facilitate the pickling operation. Other and further objects of the invention will be apparent from the following description and accompanying examples.

In the art of pickling, the metal is treated with a dilute acid to remove oxides such as rust, scale, and other deposits, after which the metal is preferably washed with water and dipped into an alkaline bath to remove the last traces of free acid. In the pickling process, the acid removes the rust and scale, but unfortunately, from the pickling standpoint, it attacks the cleaned metal itself, thereby causing loss of metal and producing an evolution of hydrogen gas, which escapes into the air, carrying with it a fine spray of the liquor from the pickling bath and producing an atmosphere possessing corrosive properties and one which is highly injurious to health and harmful to equipment.

By the present invention, these objectionable features of the pickling process are substantially overcome or reduced to a minimum. To accomplish the objects set forth in accordance with the present invention, there is added to the pickling bath a regulating agent or ingredient which acts to restrain the action of the acid from attacking clean metal but assists in removing the rust, scale and other deposits, or in other words it selectively removes such materials without appreciably attacking the clean portions of the metal.

The pickle regulator or inhibitor, as dis- Application filed October 16, 1930. Serial No. 489,240.

closed in the present application, comprises a chromic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine reaction product and preferably a chromic acid deriyatiye of a reaction product 'ofsulfEr 'dio'x de.andIEii aldehyde derivative of a SchiHs base; that is, a product formed byu'ea'c'ting' an aldehyde with a Schiifs base, adding sulfur dioxide thereto and treating the product so formed with chromic acid of any concentration necessary to produce chemical combination at the reaction temperature employed.

In the examples hereinafter set forth for carrying out the metal pickling process, conditions were imposed which duplicated, so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures employed.

Test pieces of 30 gauge low carbon hot rolled steel sheets approximately 4" x 3 in dimension were immersed in approximately 640 0.0. of a water solution of sulfuric acid containing approximately 6% by weight of 66 B. acid to which had been added a small quantity of one of the preferred type of inhibitors. The loss in weight of the steel test pieces resulting from maintaining the strips in the pickle bath in the manner described for a definite period of time was then determined. The temperature of the pickling bath was maintained at from 176 to 185 F. (80 to 85 C.). For the acid concentration set forth, commercial practice is to pickle at approximately 150 to 190 F. (66 to 88 (1.). The results so obtained were compared with similar tests wherein the steel pieces were subjected, under the conditions set forth, to the action of an acid solution of the strength and for the time specified above, but containin no inhibitor.

One method whereIiy one of the preferred class of compounds, for example a chromic acid derivative of the reaction product of sulfur dioxide and an aldehyde derivative of a Schiffs base, was prepared is as follows:

Substantially one molecular proportion of the product formed from the reaction of substantially three molecular proportions of acetaldehyde and substantially two molecuital lar proportions of aniline, according to the method set forth in U. S. Patent No. 1,659,152 granted to Clayton Olin North, was dissolved in an organic solvent, for example, a quantity of acetone equal to one-third of the weight of the aldehyde-amine product. Substantially one-half a molecular proportion of sulfur dioxide was passed thereinto at a rate slow enough for complete absorption and combination to take place while agitating and maintaining a temperature of approximately 30 to 60 C. To the product thus formed, substantially one molecular proportion of chromic acid was added at a temperature of substantially 50 to C. After the addition of the chromic acid was completed, the solvent employed, for example acetone, was removed preferably by evaporation. The product prepared in the manner described, after cooling, was a resin that was readily soluble in a pickle liquor as for example dilute sulfuric acid. A sample of the material prepared as described above was incorporated in a pickling bath in the manner hereinbefore described.

Thus, a steel test piece 3 x 4 in dimension of 30 gauge low carbon hot rolled sheets, exposing approximately 24. square inches of surface and Weighing 17 .823 grams, was found to lose but 0.318 grams after 40 min utes pickling in a 6% sulfuric acid solution containing 0.06 grams of the inhibitor hereinbefore described. A similar test piece weighing 17.928 grams and treated in the samemanner, but without the use of any inhibitor lost 7.165 grams. Thus it is shown from the above figures that when a chromic acid derivative of a reaction product of sulfur dioxide and the product formed by reacting substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline is employed as an inhibitor, the loss in weight per square inch of surface exposed is 0.01325 grams, Whereas when no inhibitor is used the loss per square inch of surface exposed is 0.2985 grams. In other words, in employing the reaction products set forth the metal loss is approximately but 4.4% as great as that resulting when no inhibitor is employed. A greater saving in metal losses results from the use of a larger amount of the inhibitor. Moreover, the steel plates pickled in the presence of the inhibitor set forth are clean and not stained upon removal from the bath.

Other chromic acid derivatives of a reaction product of sulfur dioxide and aldehyde-amine products, and preferably chromic acid derivatives of a reaction product of sulfur dioxide and aldehyde derivatives of Schiifs bases have been prepared in a manner analogous to that hereinbefore set forth and tested as inhibitors in a pickling bath in the manner described.

Thus, a chromic acid derivative of the sulfur dioxide reaction products of a Schifis base and of aldehyde derivatives thereof as set forth hereinafter were prepared in a manner analogous to that described above and the final product so obtained employed in a pickling bath and tested in the manner hereinbefore described. The products referred to in the results set forth in Table I, as inhibitors A to G inclusive, represent the chromic acid derivatives of the sulfur dioxide reaction product of the following bases:

Compound A.'Anhydr0 formaldehyde aniline.

Compound B.Reaction product of substantially three molecular proportions of butylaldehyde and substantially one molecular proportion of aniline.

Compound C.Reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of ortho-toluidine.

Compound D.Reaction product of substantially one molecular proportion of betanaphthylamine and substantially one molecular proportion of formaldehyde.

Com-pound E .Reaction product of substantially one molecular proportion of orthotoluidine and substantially three molecular proportions of butylaldehyde.

Compound F.-Reaction product of substantially one molecular proportion of 2,4- diamido diphenyl amine and substantially three molecular proportions of heptaldehyde.

Compound G'.Reaction product of substantially one molecular proportion of aniline and substantially three molecular proportions of heptaldehyde.

The results obtained by pickling steel test strips, 3 x 4" in dimension of 30 gauge low carbon hot rolled sheets for forty minutes in 640 c. c. of 6% sulfuric acid at 80 C. in the presence of one of the above described inhibitors are given in Table I.

Table l v Weight loss Weight W eight of Weight of Inhibiting com- 01 inhibsteel strip steel strip i pound employed itor embefore after i g g ployed pickling pickling exposed Grams Grams Grams Grams Compound A .06 18. 346 17. 950 0. 0165 Compound B 0.06 17.930 14. 450 0. 1450 Compound C 0.06 18. 534 18.312 0.0093 Compound D 0. 00 18. 262 18.150 0. 0047 Compound E 0.06 18.104 18. 054 0.0021 Compound F 0. 06 18. 421 18. 321 0. 0042 Compound G 0. 06 18.483 18.343 0.0058 None None. 17. 928 10. 763 0. 2985 It is thus apparent from the data set forth that the preferred class of materials constitutes an important group of inhibitors, as in all cases where one of the preferred inhibiting compounds was incorporated in the pickle liquor, there resulted a substantial decrease in the loss in weight of the steel test 252. COMPOSITIONS,

strips over that which resulted when no inhibitor was employed.

It has been found that other ratios of chromic acid, sulfur dioxide and aldehydeamine than those hereinbefore set forth may be reacted and employed as inhibitors. Thus, substantially one molecular proportion of the aldehyde derivative of a Schitfs base formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline has been reacted with substantially seventenths of a molecular proportion of sulfur dioxide and the product so formed has been reacted with substantially one-half of a molecular proportion of chromic acid. The compound thus produced was incorporated in a pickle liquor in the manner hereinbefore described, the amount of inhibitor employed and the size and grade of steel sheets used being the same as in the above described tests. A sheet weighing 18.653 grams was found after pickling forty minutes to have lost but 0.870 grams, or 0.0154 grams per square inch of surface exposed. A sheet of the same stock weighing 17.928 grams and treated in the same manner, but with no inhibitor present, suffered a loss of 7 .165 grams or 0.2985 grams per square inch of surface exposed.

Although it is desirable that the preferred inhibitor be prepared in the presence of an organic solvent, as for example acetone, benzene and the like, it is not imperative that a solvent be employed. Thus, sulfur dioxide may be reacted with the aldehyde amine product without dissolving the latter in a solvent, and the product so formed may be further reacted with chromic acid to form a compound of the preferred class and possessing the inhibiting qualities disclosed.

Other modes of employing inhibitors of the class hereinbefore set forth in the acid pickling of metals are apparent to those skilled in the art to which this invention pertains. The products described additionally may be employed in the pickling process in the presence of foaming agents, ionizable substances or other materials ordinarily used.

What is claimed is:

1. A process of pickling iron and steel products which comprises subjecting the met-- alto be pickled to the action of a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

2. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

3. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiifs base.

4. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dixoide and an aliphatic aldehyde derivative of a Schiffs base.

5. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a. small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a primary aromatic amine.

6. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular pro portions of acetaldehyde with substantially two molecular proportions of aniline.

7. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a product formed by reacting substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the product thus formed with substantially one molecular proportion of chromic acid.

8. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a product formed by reacting in the presence of acetone substantially one-half a molecular proportion of' sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of chromic acid.

9. A process of pickling a metal which comprises subjectin the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

10. A process of picking a metal which comprises subjecting the metal to be pickled to the act-ion of a substantially non-oxidizing acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

11. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of achromic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

12. A pickling bath for iron and steel products comprising a sulphuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehydearomatic amine reaction product.

13. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a. chromic acid derivative of a reaction product of sulfurdioxide and an aldehyde derivative of a Schiifs base.

14. A pickling bath for iron and steel products comprising a. sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiffs base.

15. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a. small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a primary amine.

16. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline.

17 A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a product formed by reacting substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially tWo molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of chromic acid. 4

18. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a product formed by reacting, in the presence of acetone, substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of chromic acid.

19. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a. chromic acid derivative of a reaction product of sulfur dioxide and analdehyde-amine product.

20. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a chromic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product. I

In testimony whereof I hereunto afiix my signature.

DEAL H. TOMPKINS. 

